Casing for electrical measuring instruments



' 1,631,606 June 1927' w. M. SCOTT E CASING FOR ELECTRICAL MEASURINGINSTRUMENTS Filed Jan. '7, 1922 2 Sheets-Sheet 1 June 7, 1927.

1,631,606 w. M. SCOTT ET AL CASING FOR ELECTRICAL MEASURING INSTRUMENTSFiled Jan. 7, 1922 2 Sheets-Sheet 2 Patented June 7, 1927.

UNITED STATES PATENT OFFICE.

WALTER M. SCOTT, OFLAKEWOOD, AND RALEIGH E. TRESISE, OF CLEVELAND, OHIO.

Application 1116a January 7, 1922. Serial NO. 527,552.

This invention relates to electrical measuring instruments and hasparticular reference to an ammeter of the type used on self propelledvehicles for indicating the rate of flow of current to and from thestarting and lighting battery.

The principal object of the present 1nvention is to provide aninstrument of this character which shall consist of a minimum number ofparts which are simple in con struction, inexpensive to manufacture andeasily and quickly assembled.

Another ob 'ect is to provide an instrument of this character whichshall be rugged and capable of withstanding the extreme vibrations towhich such instruments are sul ject-ed and yet be capable of indicatingaccu rately the rate of current flow to and from the battery.

A still further object is to provide any ainmeter which shall be soconstructed and assembled as to reduce toaininimum the possibility ofincurring .a short circuit therein.

With these various objects in view and others which will become apparentas the description proceeds, the invention COIlSlStS in the novelfeatures of construction. and in the manner of combining or arrangingthe same, all of which will be fully describedhereinafter and pointedout in the appended claims. 6 5 i The present application is, in somerespects, a continuation in partof our application Serial Number213,854, filed January In the accompanying drawings, Figs. -1 and 2 arefront and rear elevations, respectively, of our improved ammeter; Fig. 3is a rear elevation of the assembled operating mechanism thereforremoved from the casing; Fig. 4 is a side elevation of the parts shownin Fig. 3; Fig.6 is asectional view taken on the line 55 of Fig. 6; Fig.dis a central transverse sectional view through the instrument shown inFigs. 1 and 2; Fig. 7 is a perspective view of one of the elementsentering into the construction of the instrument; Fi 8 is a top. lanview and Fig. 9 is a side elevation o the glass-retaining ring; Fig. .10is afragmentary elevation of the rear of the instrument, showing one ofthe featuresof construction thereof; Fig. 11 is a perspective. view ofthe insulating bridge enteringinto the construe tionoif oueinstrument;Fig. l2fisa per shown in detail in Fig. 12. This supporting membercomprises a-base t-having an arm 5 projecting upwardly therefrom at eachend. Each arm is provided with an ear 6 stamped therefrom, said earslying in the plane of the base 4 and receiving screws 7 which fasten thesupporting member to the dial, the dial constituting a base for saidmember. A support 8 is struck up from the base 1, the upper portion ofsaid supportbeing bent over parallel with the base, as shown at 8, thebaseand the part 8 serving to receive and pivotally support the staff 9of an indicating needle 10. The stafi 9has mounted thereon an armature11 and a damping device 12, said damping device being located in oradjacent to a point of high concentration of a permanent mag net fieldwhich tends to resistrapid and vi-.

bratory movementof the needle and the armature 11 being spaced from saiddamp mg devlce and located in the maximum field of a current coil tobereferred to hereinafter. The opening in the base, formed by punching theneedle support therefrom] is enlarged slightly and is provided about itsperiphery with a plurality of clips 18 enabling the permanent magnet 14to be inserted into said opening from the under sideof the base and tobe retained in posiclips 13, when the parts are wardly and inwardly toform clips entering recesses 18 formed in the said bridge (see Figs. 3,11 and 12) thereby to secure said bridge to the'said arms. ,Theinsulating bridge .is provided with two apertures 19 arranged ,in spacedrelationship and adapted to receive terminal screws 20. These screwsserve as terminals for the meby soldering; I r

, the apertures The current coil preferably consists of a convolution 24and a convolution -25 spaced apart and connected by an intermediate portion 26,. the yconyolutions 2a and 25 gbe ng spaced apart and arrangedsubstantially as shown. It will henoted that the permanent magnet 1current coil 22, and the movable system comprising the staff 9, needle10, armature 11 and clamping device 12v are grouped and arranged so thatthe current coil lies wholly to one side of the permanent magnet withits field parallel to the magnet face and substantially perpendicular toa line joining the magnet poles; Also the staff 9 is mounted so as tointersect the cur-- rent coil and its axis is perpendicularto the fieldof said coil and to the plane of the magnet. This arrangement aspreviously stated, positions the damping device 12 between or adjacentthe magnet poles, orin or adjacent the point of highconcentration of thepermanent field, and also positions the arn'iature 11 in the maximumfield of the current coil and out of the maximum field of .the permanentmagnet, which causes a' more nearly equal effect by the two fields thanhas heretofore been accomplished in instrim ients of this type, and amore uniform scale is obtainable together with remarkable accuracy.

The dial, supporting member, and associated parts forming an assemblysuchas shown in Figs. 3 and 4c, are next placed in a casing. This casingis composed of a rear r portion and a front portion 31 having atransparent pane positioned therein. The rear portion 30 is providedwith two enlarged apertures 33 through which the terminal screws 20project loosely, and an inwardly directed tongue 34: is punched from thecasing adjacent to and intersecting the periphery of each aperture 33.The tongues 34L are adapted to enter aligning recesses 35,-.

35in the insulating bridge (Fig. 11 as clearly showniiji Fig. 6. andthus position the terminals 20 centrally with respect to I 33. Thisarrangement also prevents the movement of the terminals with respect tothe casing and hence prevents the rearportion of the casing fromcontacting electrically with the assembly positioned therein. due to thelarge air gap provided around each termin al.

Before the assembly is positioned in the rear portionof the casing, anapron 36 (Fig. 7) of insulating material is slipped over the terminals20 andinto contact with the insulating bridge, having apertures 36" forthe reception of said terminals. and end recesses 86" for the receptionof the tongues 34. This apron makes short1ng impossible between theclips 16 and the casing and between the coil and the casing; even shouldthe coil become displaced, as by violent treatment, or by overheat ilg,in

such a manner as to touch the base or (but for such apron) to touch thehack of the casing. When the complete assembly has been positioned inthe rear portion of the casing, and the tongues 34 are entered in therecesses .36 ant .35, as previously de scribed, then an insulatingwasher 38 is and intersect the outer edge of said flange,

as shown in Figs. 2 and 10. I

' The front portion of the casing consists essentially of an annularring comprising an inner annular seat 4C2 from which extends a flange43. The seat 4-2 is adapted to receive a transparent pane 44 therein andthis pane is retained by a spring washer 45 (Figs. '8

and 9) interposed between the front andrear portions of the casing andhaving an external annular flange 4C5 adapted to be seated between theflanges 40 and d2 andan internal flange projecting therefrom andcontacting with the periphery of said pane, as shown in Fig. 6. In thismanner the pane Oil is held securely and prevented from rattling and iseasily removed and replaced. The flange 43 isprovlded with a pluralityof apertures 4:? which are adapted to align with p the apertures 41formed in the flange 46 when the device is completely assembled. Theperipheral edge of the. flange 43 is rolled over, as indicated at 48,anzd't'his edge.

is providedwith a plurality of clips 49.

In assembling the front and rear portions of the casing, the pane isfirst insertedin the seat 42 from the rear side, theirthe spring Washer45 is placed in contactwith'tlie pane. The rear portion ofthe casingcontaining the meter assembly is then placed in contact with the frontportion of the casing so that the clips lflare in alignment with theapertures 41, which permits the flange 4:0 to be seated flush with therolled edge of'flange 43. By rotating therear portion of the casing withrespect to the front portion tl1ereof,'tl1e clips 49 will ride along theperipheral edge of the flange 40 and secure the. parts together.

'anfap'erture' therein, of a seating member ill) having a peripheralfla'nge resting on the first mentioned flange and having within saidflanges a yielding seat, a pane on said seat, and a. clamping memberhaving an inner seat for said pane and a peripheral flange locatedexternally of said seat, the peripheral flange of said clamping memberbeing formed with an aperture therein, thev outer edge of the lastmentioned flange being laterally extended to embrace the peripheral edgeof the first mentioned flange and being provided with a plurality ofprojections formed upon such lateral extension adapted to entercorrespondingly located slots in the edge of the first mentioned flange,thereby to permit the first mentioned member and the clamping member tobe secured together by relative rotary movement therebetween and bringsaid apertures in alignment to permit a fastening element to be insertedtherethrough.

2. In an instrument of the class described, the combination, with acasing member having a peripheral flange, of a seating mem ber having aperipheral flange resting on the first mentioned peripheral flange andprovided with an interior seat, a pane on said seat, and a clampingmember having an interior flange engaging the outer peripheral portionof said pane and an exterior flange having its peripheral edge rolledover to engage said first mentioned flange to secure said seating memberto said casing member.

3. In an instrument of the class described, the combination, with acasing member having aperipheral flange having a plurality of spacedslots therein, a seating member having a flange resting on saidperipheral flange and provided with an interior seat, a pane on saidseat, and a clamping member having an interior seat for the peripheralportion of said pane, said clamping member being provided with aplurality of apertures adapted to be aligned wtih said slots in saidcasing member whereby to receive a screw for securing said casing memberand clamping member together, the outer peripheral edge oi said clampingmember having a plurality of projections thereon bent over and adaptedto enter said slots and to engage said first mentioned flange uponrelative rotary movement of said members. 7

l. In an instrument of the class described, the combination, with acasing comprising two members, each having a peripheral flange, one ofsaid flanges having a plurality of slots therein and the other of saidmembers having a plurality of apertures therein adapted to be alignedwith said slots, said last mentioned member having its peripheral edgerolled over to embrace the edge of said first mentioned fla'nge and aplurality of projections formed on said rolled edge and adapted to entersaid slots and to engage the first mentioned flange through relativerotary movement of said members, whereby to secure said memberstogether.

5. In an instrument of the class described, the combination with acasing member having a peripheral flange provided with a plurality ofspaced slots extending to and in eluding the edge thereof, a clampingmember having an external peripheral flange provided with spacedapertures therein adapted to be aligned with said slots, said lastmentioned flange being rolled over to embrace the edge of said firstmentioned flange, and a plurality of projections formed on such rollededge adapted to enter said slots and to engage the first mentionedflange through relative rotary movement of said members whereby tosecure said members together.

6. A casing for an instrument of the character set forth comprising twomembers, the abutting edges of each of said members be ing provided eachwith a flange and each of said flanges being provided with a pluralityof apertures, the apertures in one of said flanges being adapted toalign with the apertures in the other of said flanges, a plurality ofprojections formed on one of said flanges, the other of said flangeshaving a plurality otnotches therein extending to and including the edgethereof, said projections being adapted to enter the last mentionednotches and engage the other flange through relative rotary movement ofsaid members whereby to fasten said members together and bring the firstmentioned notches in alignment whereby to receive means for preventingrelative rotation of said members.

7. In an instrumento'f the class described,

the combination of-a casing having an annular peripheral flange, of aseating member having a portion resting on said peripheral flange andadapted to form a seat for a glass pane, of a clamping member having aninterior flange engaging the outer peripheral portion of said pane andan exterior flange projecting over and cooperating with the peripheralflange on said casing to secure said pane to said casing, saidlast-mentioned peripheral flange having its peripheral edge rolled overto embrace the edge of said first mentioned flange, said first mentionedflange having a plurality of notches in its edge and said rolled overedge having a plurality of projections thereon bent so as to enter saidnotches and to engage the rear side of saidv first mentioned flangethrough relative ro-- tary movement of said casing .and clamping member.

In testimony whereoi. we hereunto affix our signatures.

' WALTER M. SCOTT.

RALEIGH E. TRESISE.

